Interindividual differences in CCR5 expression levels are a critical determinant of HIV-1 susceptibility and progression rate to AIDS. There is strong evidence indicating that these differences could be ascribed to genetic variation in the CCR5 locus. Genetic variability in CCR5 also has been implicated in susceptibility to other infectious and systemic diseases that are relevant to the veteran population. Delineating the mechanisms that modulate intersubject differences in CCR5 expression levels is thus of indisputable importance and significance for understanding pathogenesis of HIV-1 infection and other diseases such as diabetes. There is strong in vitro and in vivo evidence that the polymorphic residues at positions -2135 and -2459 in the CCR5 cis-regulatory region have a dominant effect on its expression. Our studies in this proposal are designed to elucidate the mechanisms by which differential binding of transcription factors to these polymorphisms leads to allele-specific modulation of gene expression resulting in variable CCR5 levels. Specific Aim 1 will test the hypothesis that disease-modifying CCR5 alleles exhibit variable transcription factor binding repertoire. Specific Aim 2 will determine whether the TFs that bind differentially to CCR5 SNPs also influence variable CCR5 expression. We will employ state-of-the art and innovative proteomic and molecular techniques to dissect the complex interactions between the TF binding to CCR5 polymorphisms which lead to variability in CCR5 expression levels. These studies have translational (benchAEbedside) utility as they will identify mechanisms of variable CCR5 expression that may impact on susceptibility to HIV-1/AIDS and other diseases. These molecular studies will capitalize on the vast experience of the PI in transcriptional gene regulation and collaborative efforts with Dr. Jarrett, a leading authority in transcriptional proteomics. There are several down-stream, value-added features of this application: (a) although the studies outlined in this grant will focus on the transcriptional proteomics of CCR5, they are widely applicable to a broad array of genes for which regulatory variation has been implicated in human disease; (b) the results may identify new pathways to target CCR5 expression, thus resulting in development of new therapies; (c) identification of additional genetic determinants that influence CCR5 expression levels. The outlined studies might lead to development of effective treatment strategies and improved vaccination trials and are in line with the goals of VA's Genomic Medicine Initiative.